JQuery Append to a child element

I have a jQuery like this.

$.each($(".fc-daygrid-day "), function (key, val) {
  var dateYMD = $(this).attr("data-date");
  console.log(this); 
  $(this).append(`<div class="fc-dailytotal" id='dailytotal-" + dateYMD + "'></div>`);
});

Which returns something like this. ( this is what I get when I console.log(this) )

<td class="fc-daygrid-day fc-day fc-day-thu fc-day-future fc-day-other" data-date="2020-11-05">
  <div class="fc-daygrid-day-frame fc-scrollgrid-sync-inner"> <!-- line 2 -->
    <div class="fc-daygrid-day-top"><a class="fc-daygrid-day-number">5</a></div>
    <div class="fc-daygrid-day-events"></div>
    <div class="fc-daygrid-day-bg"></div>
  </div>
  <div class="fc-dailytotal" id="dailytotal-&quot; + dateYMD + &quot;">0</div> <!-- line 1 -->
</td>

I want to append the line 1 inside the line 2 div tag ? final result i want is as following. Thank you. (i am new to JQuery)

<td class="fc-daygrid-day fc-day fc-day-thu fc-day-future fc-day-other" data-date="2020-11-05">
  <div class="fc-daygrid-day-frame fc-scrollgrid-sync-inner"> <!-- line 2 -->
    <div class="fc-daygrid-day-top"><a class="fc-daygrid-day-number">5</a></div>
    <div class="fc-dailytotal" id="dailytotal-&quot; + dateYMD + &quot;">0</div> <!-- line 1 -->
    <div class="fc-daygrid-day-events"></div>
    <div class="fc-daygrid-day-bg"></div>
  </div>
</td>

You can use find() to target the child element and then after() to insert the content to be displayed directly below it. Also note that your string concatenation syntax is incorrect. As you're using a template literal you need to use ${foo} to insert the value in to the string. Try this:

$.each($(".fc-daygrid-day"), function (key, val) {
  var dateYMD = $(this).attr("data-date");
  $(this).find('.fc-daygrid-day-top').after(`<div class="fc-dailytotal" id='dailytotal-${dateYMD}'></div>`);
});

In addition it's worth noting that the code can be improved. Firstly use data() to read a data attribute so that the result is more strongly typed. Also, given what you're actually attempting to achieve you don't need an explicit each() loop at all. You can provide a function to after() which generates the content dynamically.

$('.fc-daygrid-day .fc-daygrid-day-top').after(function() {
  let dateYMD = $(this).closest('.fc-daygrid-day').data('date');
  return `<div class="fc-dailytotal" id="dailytotal-${dateYMD}">Example: ${dateYMD}</div>`
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<table>
  <tbody>
    <tr>
      <td class="fc-daygrid-day fc-day fc-day-thu fc-day-future fc-day-other" data-date="2020-11-05">
        <div class="fc-daygrid-day-frame fc-scrollgrid-sync-inner">
          <div class="fc-daygrid-day-top"><a class="fc-daygrid-day-number">5</a></div>
          <div class="fc-daygrid-day-events"></div>
          <div class="fc-daygrid-day-bg"></div>
        </div>
      </td>
    </tr>
    <tr>
      <td class="fc-daygrid-day fc-day fc-day-thu fc-day-future fc-day-other" data-date="2021-12-15">
        <div class="fc-daygrid-day-frame fc-scrollgrid-sync-inner">
          <div class="fc-daygrid-day-top"><a class="fc-daygrid-day-number">10</a></div>
          <div class="fc-daygrid-day-events"></div>
          <div class="fc-daygrid-day-bg"></div>
        </div>
      </td>
    </tr>
  </tbody>
</table>